The present invention relates generally to drilling fluids and specifically to a viscosifier for oil base drilling fluids of the type used in well completion and workover operations.
During the drilling of oil and gas wells, drilling fluid is circulated in the well bore to cool and lubricate the drill bit and pipe, to carry cuttings from the bottom of the well bore to the surface, and to impose a hydrostatic head on the drilled formation to prevent the escape of oil, gas, or water from the well bore.
The term "oil base drilling fluid" is applied to drilling fluids in which oil is the continuous phase and water, if present, is the dispersed phase. An oil base fluid or mud commonly comprises blown asphalt and usually a small amount of water emulsified into the system with caustic or lime and emulsifying agents. The dispersed asphalt increases the density of the oil and provides needed viscosity and gel strength to properly suspend weighting materials, cuttings, and other solids in the fluid.